/// <summary>
        /// 获取指定名称的块属性值
        /// </summary>
        /// <param name="blockReferenceId">块参照的Id</param>
        /// <param name="attributeName">属性名</param>
        /// <returns>返回指定名称的块属性值</returns>
        public static string GetAttributeInBlockReference(this ObjectId blockReferenceId, string attributeName)
        {
            string attributeValue = string.Empty; // 属性值
            Database db = blockReferenceId.Database;
            using (Transaction trans = db.TransactionManager.StartTransaction())
            {
                // 获取块参照
                BlockReference bref = (BlockReference)trans.GetObject(blockReferenceId, OpenMode.ForRead);
                // 遍历块参照的属性
                foreach (ObjectId attId in bref.AttributeCollection)
                {
                    // 获取块参照属性对象
                    AttributeReference attRef = (AttributeReference)trans.GetObject(attId, OpenMode.ForRead,true);
                    //判断属性名是否为指定的属性名
                    if (attRef.Tag.ToUpper() == attributeName.ToUpper())
                    {
                        attributeValue = attRef.TextString;//获取属性值
                        break;
                    }
                }
                trans.Commit();
            }
            return attributeValue; //返回块属性值
        }